Motors, particularly internal combustion motors generate high levels of noise and require some form of sound insulation before they are acceptable by the general public. Where space permits, enclosures are built around such motors and sound absorbing material is installed within the enclosure to reduce or redirect the sound level particularly in the area occupied by the user of the motor, or others nearby. Typically such enclosures are generally rectangular boxes or fitted covers designed to fit closely to the motor itself, with slabs of insulation material affixed to the inside wall of the enclosure. When the enclosure provides generally large flat surfaces joined at 90°, slab insulation is usually not too difficult to apply and the results are reasonably effective.
Unfortunately sound insulation using slab material becomes less effective when the casing of the motor is no longer a square box but due to design requirements comprises curved, particularly compound curved surfaces. Such, for example, is the situation of an outboard engine commonly used to power a large number of boats. In such applications, slab insulation requires the use of a large number of sound insulating material pieces to cover the inside surface of the casing. Such sound reduction method is expensive to implement and is not very effective as it tends to leave gaps through which sound escapes thereby reducing the effectiveness of the sound insulation package.
In addition, it has been observed that at times and for certain frequencies, the cover panels of the motor enclosure vibrate and further amplify the engine sounds. There is, therefore, still considerable need for improvement in this area, both from the economic point of view as well as the effectiveness of the sound reduction.